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libstdc++: Simplify constraints for std::any construction [PR104242] 

Partially revert r12-4190-g6da36b7d0e43b6f9281c65c19a025d4888a25b2d
because using __and_<..., is_copy_constructible<T>> when T is incomplete
results in an error about deriving from is_copy_constructible<T> when
that is incomplete. I don't know how to fix that, so this simply
restores the previous constraint which worked in this case (even though
I think it's technically undefined to use is_copy_constructible<T> with
incomplete T). This doesn't restore exactly what we had before, but uses
the is_copy_constructible_v and __is_in_place_type_v variable templates
instead of the ::value member.

libstdc++-v3/ChangeLog:

	PR libstdc++/104242
	* include/std/any (any(T&&)): Revert change to constraints.
	* testsuite/20_util/any/cons/104242.cc: New test.
This commit is contained in:
Jonathan Wakely 2022-03-18 13:10:01 +00:00
parent c5086228cd
commit 7a42b1fa1a
2 changed files with 14 additions and 2 deletions
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4
libstdc++-v3/include/std/any
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@ -185,8 +185,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// Construct with a copy of @p __value as the contained object. /// Construct with a copy of @p __value as the contained object.
template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>, template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>,
typename _Mgr = _Manager<_VTp>, typename _Mgr = _Manager<_VTp>,
typename = _Require<__not_<__is_in_place_type<_VTp>>, enable_if_t<is_copy_constructible_v<_VTp>
is_copy_constructible<_VTp>>> && !__is_in_place_type_v<_VTp>, bool> = true>
any(_Tp&& __value) any(_Tp&& __value)
: _M_manager(&_Mgr::_S_manage) : _M_manager(&_Mgr::_S_manage)
{ {

12
libstdc++-v3/testsuite/20_util/any/cons/104242.cc Normal file
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@ -0,0 +1,12 @@
// { dg-do compile { target c++17 } }
// PR libstdc++/104242 - Class with constructor from std::any is not copyable
#include <any>
#include <type_traits>
struct A {
A(const A&) = default;
explicit A(std::any value);
};
static_assert(std::is_copy_constructible_v<A>);